A Contribution to the Petrology of Kerguelen. 213 



The prevailing felspar is sanidine, which occurs in rather large 

 ci'ystals. It is modified just as in the rock No. 6. Hornblende 

 is in considerable quantity, and it has undergone a modification 

 similar to that in the rock just described. Augite is sparingly 

 distributed. Apatite and sphene occur. There are a few altered 

 crystals present which from their sections suggest nepheline ; 

 alteration has, however, taken place to such an extent as to make 

 the microscopic determination of this mineral uncertain. In 

 addition to secondary zeolitic matter, there is also some secondary 

 silicious matter tilling cracks and cavities in the slide ; when 

 visible in cavities it has a radially tibrous structure. The rock 

 may possibly be an altered phonolite. 



